Turbo ventilation utilizing baffles in air gap



March 30 1926. 1,578,577

D. BRATT TURBO VENTILATION UTILIZING BAFFLES IN AIR GAP F'iled June 1923 Z! Z! 1 0 Q I l 1)] Fig. 4.

Radial Velodifies WITNESSES: I v INVENTOR 'Dongld Brqfi'.

" .IATTORNEY'I Patented Mar. 30, 1926.

PATENT SFFIQE.

DONALD BRATT, OF IRWIN, PENNSYLVANIA, ASSIGNOR TO WESTINGHOUSE ELECTRIC & MANUFACTURING COMPANY, A CORFORATION 0F PENNSYLVANIA.

TURBO VENTILATION UTILIZING BAFFLES IN AIR GAP.

Application filed June 26, 1923. Serial No. 647,784.

To all whom, it may concern:

Be it known that I, DONALD Bnivr'r, a subject of the King of Sweden, and a resident of Irwin, in the county of lVestmoreland and State of Pennsylvania, have invented a new and useful ln'iprovenient in Turbo Ventilation Utilizing Battles in Air Gaps, ct which the following is a specification.

My invention relates to the ventilation of dynamo-electric machines and it has particular relation to the type of machine which is ventilated by means of air admitted to the periphery of the stator as well as air admitted to the ends of the air-gap, the ventilation being secured by a circulation radially through ventilating ducts in the stat-or and axially through the air-gap.

An object of my invention is to provide a practical means for inserting readily removable ballle members in the air-gap for controlling the distribution of radial air veloc ity in the stator ventilating ducts.

Another object of my invention is to provide a plurality of bolts on the periphery of the rotor member and within the air-gap for serving the function of baliie rings in the air-gap. I

A further object of my invention is to provide a plurality of vanes on the periphery of the rotor member and within the air-gap for assisting or retarding the axial flow of air past the vanes.

A still "further object of my invention is to provide such means in a ventilating system wherein the maximum uniformity of radial air velocity is secured.

With the foregoing and other objects in view, my invention consists in the construction and arrangement hereinafter described and claimed, and illustrated in the accompanying drawing, wherein I Fig. 1 is a longitudinal sectional view .11- lustrating a turbo-alternator embodying my invention,

Fig. 2 is a diagrammatic transverse view of the rotor member showing bolts of a modified form thereon,

Figs. 3 and 4 are enlarged sectional elevation and plan views of a bolt having a head comprising a vane as shown in Fig. 1, and

Fig. 5 is a curve drawing illustrating the principles of application of my invention.

In Fig. 1 is shown a turbo-alternator comprising a stator member 10, carrying alternating-current windings 11, and a rotor member 12, carrying direct-current field windings, the end turns of which are shown at 13. The stator and rotor members are both of the smooth core type, and they are separated by an air-gap 14.

The stator member 10 comprises a laminated magnetizable core 15 having a large number of radial ventilating spaces 16 left between bunches of laminations 17 The radial'ventilating spaces or ducts are dividedinto a plurality of groupssurrounded by annular chambers 18, 19 and 20, the corn tral and end chambers 20 and 18 being discharge chambers having discharge vents 21,

and the intermediate chamber 19 being an intake chamber for forcing a cooling fluid radially inwardly through the corresponding radial spaces 16. 1

Cooling fluid is supplied to the end bells otthe machine by any suitable means, such as fans 23 which are secured to the ends of the rotor member 12. The intake chambers 19 are likewise supplied with cooling fluid by any suitable means, such as ducts 24 connecting the same to the respective end-bell spaces.

The general operation of the ventilating system shown in Fig. 1 willbe obvious. Cooling fluid admitted from the ends of the air-gap passes out through the nearest radial ducts 16 into the annular discharge chambers 18. Cooling fluid admitted from the annular intake chambers 19 passes radially inwardly to the air-gap andthence divides and discharges through the radial ducts 16 associated with the adjacent annular discharge chambers 18 and 20,.all as indicated by the arrows.

The function of cooling is performed mainly by the radially moving air in the radial ventilating spaces rather than by the axially moving air in the air-gap, and prior structures of the type hereinabove described have been subject to the objection that the air admitted from the ends of the air-gap travels at such a high initial velocity that it does not have a suilicient pressure head to cause a sutliclent radial How in the first few vradial ventilating spaces of the stator member. Furthermore, the air admitted from the ends of the air-gap disturbs the balance or symmetry of the radial'velocity distribution in all of the sections except the center sect-ion and it very greatly increases the differences between the maximum and minimum radial velocities. A typical curve illustrating the conditions in machines of the type known in the prior art is indicated in dotted lines in Fig. 5, wherein the radial velocities are plotted against the length of the air-gap.

Since the principal cooling function is performed by the radially moving air, and since such cooling is dependent upon the velocity of the air, it is apparently desirable to maintain, as far as possible, balanced or symmetrical conditions in each of the sections of the stator member. It is obvious that the poor radial velocity distribution which is shown in dotted lines in Fig. 5 could be improved by means of suitable baffie rings in the airgap. Such means are not practical, however, since the herein described type of ventilation is utilized, at present, only in very large turbo-alternators, and all-of the clearance between the stator and rotor members is usually needed in order to place the rotor member in position. Furthermore, the presence of rings or other permanent battles in the air-gap would be likely 'to damage one or both of the members in the process of inserting the rotor member.

According to my invention, I provide a series of small bolts 26, arranged in a circle around the rotor member, and projecting into the air-gap to act as a barrier ring. The radial velocity imparted to the cooling air by the bolts will act as a partial screen to the air flowing axially in the gap, thereby affecting the axial subdivision of air volume in the radial vents and causing more air to flow to the radial vents on the incoming side of the bolts.

The bolts 26 are preferably arranged in a circle and there are preferably the same number of circles of bolts at each end of the rotor. The distance of the bolts from the ends of the air-gap may have any value dictated by the exigencies of any particular case and, if desirable, a plurality of rings of bolts having the'same or different sizes may be provided for directing the air to successive radial vents or groups of radial vents.

In the form of invention as shown, by

way of example, in Fig. 1, the bolts are arranged on the center line of the first section of the stator member to provide, in effect, a closure in the air-gap at such point. In such a'system, the stator ventilation resulting from the air admitted to the annular intake chambers of the staton may be laid out with aview to obtaining maximum equality of radial velocities consistent with the number of groups of intake chambers available. The ring of boltsis then placed at the ends of the half-sections comprising the end discharge radial vents'of the stator ventilation. The air-gap ventilation, utilizing air blown 111 from the ends of the airgap, may then have as many, or as few, ra-

dial vents in the. stator as may be necessary or desirable, and the main stator ventilation will notbe disturbed. In the embodiment of my invention illustrated in Fig. 1, the end half section of the stator member is shown as having the same length as the last half section of the discharge for the stator ventilation and the resultant distribution of radial velocity will'be somewhat as shown in full lines in Fig. 5. a

If desirable, the heads of the bolts 26 may be provided with vanes 27 which may be directed at any angle when the bolts are applied, in order to cause the bolts toexert an impelling or blower action for impeding or assisting the flow'of air. In general, it will be desirable for the bolts to impede the flow of air from the ends of the air-gap.

The overall length of the bolts is preferably less than the width of the air-gap, whereby the bolts may be readily removed by using any ordinary or special wrench without first entirely removing the rotor member from the stationary part of themachine. The bolts may be made of analloy steel or of other suitable non-magnetic material and are provided with threads of such pitch and diameter that a secure tightening is possible without resulting in abnormal stresses in the bolts or in the rotor underthe guaranteed overspeed condition of the rotor.

While I have described my invention in a specific form, utilizing bolts as the removable baflie means, it will be understood that any readily applicable and ren'iovable elements may be employed, and where the vanes 27 are utilized, the removable feature will not be necessary to contribute to the novelty of the application. I desire, therefore that the appended claims shall be giventhe broadest interpretation consistent with the prior art.

I claim as my invention:

1. A rotor member of a dynamo-electric machine having a belt or bolts screwed into its periphery to serve as a battle in the airgap.

2. A rotor member of a dynamo-electric machine having one or more detachable protuberances secured to its periphery to serve as a bathe in the air-gap.

A rotor member of a dynamo electric machine having one or more bolts screwed into its periphery, each of said bolts "having a vane-like head to serve as a battle in the air-gap.

I. A dynamo-electric machine comprising a stator member and a rotor member separated by an air-gap, said stator memher being provided with a plurality of radial ventilatin spaces surrounding said air-gap, means for introducing a ventilating fluid and causing the same to move axially in said air-gap and radially in said radial spaces, and a plurality of bolts disposed in a circle about said rotor member and within said air-gap, the length of the bolts being such as to admit of their removal from the air-gap.

5. A dynamo-electric machine comprising a stator member and a rotor member separated by an air-gap, said stator member being provided with a plurality of groups each comprising a plurality of radial ventilating spaces surrounding said air-gap, means for introducing a ventilating fluid and causing the same to move radially inwardly in one or more groups of radial spaces, radially outwardly in two or more groups of other radial spaces and axially in the air-gap, and a plurality of bolts disposed in a plurality of circles about said rotor member and within said air-gap for controlling the distribution of radial velocities of the ventilating fluid, the heads of said bolts having a thickness less than said air-gap;

6. A dynamo-electric machine comprising a stator member and a rotor member separatcd by an air-gap, said stator member being provided with a plurality of radial ventilating spaces surrounding said air-gap, stator ventilation means for introducing a ventilating fluid to the periphery of the stator member and for causing said ventilating fluid to move radially inwardly in some radial spaces, radially outwardly in others and axially in the air-gap, air-gap ventilation means for introducing a venti lating fluid to the ends of the air-gap, said fluid passing outwardly through the adjacent radial spaces, and a plurality of detachable protuberances secured to said rotor member in a plurality of circles within said air-gap and near the ends thereof for substantially preventing the ventilating fluid admitted from the ends of the air-gap from disturbing the stator ventilation whereby substantially balanced or symmetrical distribution of radial velocities is maintained in each of the intermediate groups of intake and discharge radial ventilating spaces and in the inner portion of the end groups of discharge radial ventilating spaces.

7. A dynamo-electric machine comprising a stator member and a rotor member separated by an air-gap, said stator member being provided with a plurality of radial ventilating spaces surrounding said air-gap, means for introducing a ventilating fluid to a plurality of annular regions around the stator member and to the ends of the airgap and for causing said ventilating fluid to move radially inwardly in some radial spaces,'radially outwardly in others and axially in the air-gap, and a plurality of vanes secured to said rotor member in a plurality of circles within said air-gap and near the ends thereof for substantially balancing the static pressures of the axially flowing ventilating fluids admitted, respectively, from the ends of the air-gap and from the periphery of the stator member, whereby substantially balanced or symmetrical distribution of radial velocities is maintained in each of the intermediate groups of intake and discharge radial ventilating spaces and in the inner portion of the end groups of discharge radial ventilating spaces.

In testimony whereof, I have hereunto subscribed my name this 14th day of June, 1923. I v

DONALD BRATT. 

